1. Field of the Invention
This invention relates to filled polymer blends and, more specifically, it relates to filled blends of ethylene/.alpha.-olefin interpolymers modified with plasticizer.
2. Description of the Prior Art
The use of processing oils and other plasticizers with natural rubber or synthetic rubber-like compounds containing sulfur, accelerators, carbon black and other additives customarily used in the rubber industry is well known. In some instances in order to obtain very high tensile strength values, fillers are omitted. On the other hand, it is known that styrene/butadiene rubber (SBR) compounds, such as are used to adhere jute secondary backings to carpets, can readily hold up to 80% by weight or more of calcium carbonate filler. Vulcanization or curing enhances blend strength.
For thermoplastic elastomeric uses, it is desirable both to avoid curing and to employ fillers to reduce blend costs, as well as to increase blend density.
Industrial noise and its control are items of increasing concern to governmental, environmental, and industrial organizations. Governmental agencies are establishing noise limits to which workers may be exposed to protect their health.
From an aesthetic standpoint, noise also presents problems. Advertisements for "quiet riding" automobiles are ubiquitous. Manufacturers are attempting to make other vehicles quiet as well--including campers, trailers, buses, trucks, and off-road-use farm vehicles.
It has long been known that interposing mass between a sound source and the area to be kept quiet is an effective means for attaining sound deadening. A sheet of lead is thin, flexible, often highly effective, but costly. The challenge, then, is to attain a dense, thin, flexible sheet which can be interposed between a source of noise and the area to be quietened.
Sheets of thermoplastics or of rubberlike materials have long been used as sound-deadening means. To make the sheets flexible, dense, strong, and inexpensive has posed a challenge to compounders for many years. For some uses, such as automobile carpet underlayment, the sound-deadening sheet must also be moldable.
Schwartz U.S. Pat. No. 3,904,456 is related to a method for inhibiting transmission of airborne noise by interposing in the air space between the noise source and the location to be insulated a thin, dense, normally self-supporting film or sheet composed essentially of from about 10 to about 40% by weight of ethylene/vinyl acetate copolymer having an average vinyl acetate content of from about 10 to about 42% by weight and a glass transition temperature of at least about 30.degree. C. below the average ambient temperature in the air space, and from about 60 to about 90% by weight of inorganic filler materials, such as sulfates, carbonates, oxides, etc. of barium, calcium, cadmium, etc., effective to produce an overall density greater than at least 2 grams per cubic centimeter.
German Patent Application No. 2,319,431 discloses sound-deadening composites suitable for use in automobiles which consist of a highly filled polymer sheet (for example, 300-1200 or even up to 1500 parts of filler per 100 parts of polymer) which on its backside is provided with a filler material sheet, e.g., a polymer foam. Suitable polymers for use are disclosed to be terpolymers of ethylene, propylene and a nonconjugated diene (EPDM), polyvinyl chloride (PVC), mixed polymers of ethylene and vinyl acetate (EVA), styrene-butadiene mixed polymers (SBR) and mixtures of these materials with thermoplastic polymers, such as polystyrene and polyolefins.
Rosenfelder U.S. Pat. No. 3,203,921 discloses the use of compositions consisting essentially of 73-88% by weight of a homo- or copolymer of ethylene (which can be ethylene/vinyl acetate or ethylene/ethyl acrylate copolymer), 2-7% by weight of an aliphatic paraffinic hydrocarbon mineral oil and 10-20% by weight of a mineral filler (for example, calcium carbonate, barium sulfate, etc.) for preparing blow-molded objects such as dolls.
Schumacher and Yllo U.S. Pat. No. 4,191,798 discloses compositions consisting essentially of 5-50% by weight of ethylene interpolymer (e.g., ethylene/vinyl acetate copolymer), 2-15% by weight of processing oil, and 50-90% by weight of filler. These compositions have utility when formed as sound-deadening sheet and to have particular utility as a backside coating on automotive carpets.
Belgian Patent No. 694,890 entitled "Surface Hardening Plastics Based on Ethylene/Propylene Elastomers" discloses blends of ethylene/propylene copolymer, mineral oil, filler and a drying oil for use as a surface hardening mastic, where the copolymer contains 25-75 mole percent propylene (about 33-82 weight percent). These blends are claimed to be useful in sealing mastics in buildings and metal constructions.
Japanese Patent Publication No. 042-235/78 (Japanese Application No. 118114/76) discloses hot melt compositions comprising an ethylene/.alpha.-olefin copolymer, a hydrocarbon oligomer, a hindered ester, 1-10 percent by weight of colloidal silica and microcrystalline wax. Although these compositions contain mainly olefinic compounds, it is asserted that flexibility and internal loss are maintained while adhesion to olefinic-type film is prevented. The compositions are disclosed to be useful for vibration damping.
U.S. Pat. No. 3,963,802 is related to blends of certain ethylene copolymers and segmented copolyether ester elastomers in specific proportions. Suitable ethylene copolymers are disclosed as those having one or more comonomers selected from the group consisting of alpha-olefins and nonconjugated diolefins, said copolymer having a melting point not greater than 85.degree. C. A suitable copolyether ester is disclosed as consisting of 15-95 percent by weight of short chain ester units and 5-85 percent by weight of long chain ester units, said copolyether ester having a melting point of at least 100.degree. C. It is disclosed that the copolyether ester elastomer is made softer, with retention of toughness and other physical properties, by blending with the ethylene copolymer. It is further disclosed that from 1 to 30 percent by weight of fillers and pigments (e.g., very finely divided silica, alumina, or calcium carbonate) may be incorporated in the blend to increase the toughness and temperature resistance.